Add Rails Webpacker as alternative to CRA in Rails (facebook#3868)

* Add Rails Webpacker as alternative to CRA in Rails

* Update README.md

README.md

@@ -192,7 +192,7 @@ Here’s a few common cases where you might want to try something else:
 
 * If you want to **try React** without hundreds of transitive build tool dependencies, consider [using a single HTML file or an online sandbox instead](https://reactjs.org/docs/try-react.html).
 
-* If you need to **integrate React code with a server-side template framework** like Rails or Django, or if you’re **not building a single-page app**, consider using [nwb](https://github.com/insin/nwb) or [Neutrino](https://neutrino.js.org/) which are more flexible.
+* If you need to **integrate React code with a server-side template framework** like Rails or Django, or if you’re **not building a single-page app**, consider using [nwb](https://github.com/insin/nwb), or [Neutrino](https://neutrino.js.org/) which are more flexible. For Rails specifically, you can use [Rails Webpacker](https://github.com/rails/webpacker).
 
 * If you need to **publish a React component**, [nwb](https://github.com/insin/nwb) can [also do this](https://github.com/insin/nwb#react-components-and-libraries), as well as [Neutrino's react-components preset](https://neutrino.js.org/packages/react-components/).